Babies and substrate dampness

[Diana Stone]

I am wondering how damp the substrate should be for hatchlings. They are on a mix of bed-a-beast and cypress mulch. I know they should have some humidity but not certain how damp the substrate should be to get the right amount. Should I be spraying it a couple times a week and make sure it gets to the bottom to keep that damp?
And one other question please. Should the night time temp be no lower than 70? My house is 70 at night but the temp in thier enclosure is about 65, probably due to the humid substrate?

thanks for your help.